Weed control in wheel tracks

Improving weed control in wheel tracks during summer fallow spraying

Poor weed control in the wheel tracks of the sprayer can result from a number of factors, such as those listed below, which often interact with each other.

• The additional stress placed on the weeds due to the physical damage from being run over. This leads to poorer uptake and translocation of many products.
• Poor deposition of spray, resulting from droplets being pushed away from the wheel track by air displaced by the sprayer’s tyres. This effect increases with higher travel speed, wider tyres and more aggressive lug patterns.
• More dust produced by higher travel speeds and dry soil can interact with many products on the leaf surface (such as glyphosate and paraquat), potentially reducing their efficacy.

These factors should not be confused with secondary germinations of weeds that may occur shortly after the application.

Key points

• Poor control of weeds in the sprayer’s wheel tracks and the adjacent areas during summer fallow applications can be the result of poor spray deposition, excessive dust, or a combination of the two.
• Using additional wheeltrack nozzles for knockdown herbicides (non-residual) can improve deposition and the level of control in the wheel tracks and adjacent areas.
• Generally, dust is only reduced when soil moisture is present, speed is reduced or more permanent wheel tracks are used.